Field of the Invention
The present invention relates to a gray level control method and an optical projection system, and in particular to a gray level control method and an optical projection system capable of utilizing the bandwidth of a light modulator effectively, improving the overall brightness, and lowering the switching frequency of a light source.
Description of the Related Art
A projector technique is using pulse width modulation (PWM) to control the number of times that a light modulator (for example, a digital micro-mirror device) is switched to form a gray level of a projection image. A naked-eye 3D projector is an important development direction of the present projector. When the naked-eye 3D projector uses multiple light sources and a time-division multiplexing method to output multi-view images, the number of images displayed within in a display period is proportional to the switching frequency of the light modulator. However, the switching frequency of the light modulator, for example, a digital micro-mirror device, has physical limitations which limit the number of images.
In order to utilize the limited bandwidth of a light modulator, pulse width modulation or pulse amplitude modulation (PAM) can be further applied to modulate the brightness of the light source to lower the switching number the light modulator needs for outputting a gray level. However, this method makes the light source change its brightness in accordance with switching time of the light modulator, so the overall light is lowered. In addition, rapidly switching a light source also has physical limitations.
In view of this, the invention provides a gray level control method and an optical projection system capable of utilizing the bandwidth of a light modulator effectively, improving the overall brightness, and lowering the switching frequency of a light source.